Separable bolt



June 17, 1969 ALBERT T. TAKAHASHI 3,449,996

SEPARABLE BOLT Filed Jan. 12, 1966 11: a gnu n llll u udi dlm w 1 N VENTOR.

ALBERT 7. TAKAHASH/ ATTOE/VEKS.

June 17, 1969 ALBER'T T, TAKAHASH. 3,449,996

SEPARABLE BOLT Filed Jan. 12, 1966 Sheet i of 2 FIG. 6 58 INVENTOR. ALBERT 7'. TAKAHASH/ United States Patent 3,449,996 SEPARABLE BOLT Albert T. Takahashi, Torrance, Calif., assignor to Hi- Shear Corporation, Torrance, Calif., a corporation of California Filed Jan. 12, 1966, Ser. No. 520,258

Int. Cl. F16b 29/00 US. Cl. 85-1 6 Claims ABSTRACT OF THE DISCLOSURE This invention relates to separable bolts. It includes means for amplifying the pressure from a source of fluid under pressure, and to separate the bolt by a purely axially push which causes separation of the bolt by tensile failure, the level of which failure is readily determinable by appropriate selection of cross-section area at a point of least cross-section.

This invention relates to separable bolts.

Many times it is desired to hold two objects together in relative proximity by a bolt, and to have the capability of releasing the two objects from each other at a desired time. It has previously been known to provide explosive bolts for this purpose. Conventional explosive bolts were provided with a weakened region within which an explosive charge was placed. The separative force was the product of the lateral area of the chamber holding the explosive times the generated pressure. A suflicient charge had to be provided to assure separation, and the resulting explosion was often damaging to surrounding structure. It is an object of this invention to provide an explosive separable bolt in which suflicient separative forces are developed with minimum pressures. Furthermore, the separative force is exerted purely axially, thereby more efiiciently utilizing the fluid forces. The separation is therefore more reliable, and utilizes minimum fluid pressure levels.

An additional optional object of the invention is to exert the fluid pressure at a location spaced away from the point of separation, thereby to avoid possibly undesirable expansion of the bolt at the point of separation.

A separable bolt according to this invention includes 'a body that has a first and a second bore, these bores having an axis and being coaxial. The bores are interconnected. The body includes a neck which forms a bolt, the first bore extending into the neck. A groove is formed in the neck so as to form a region of reduced cross-section with the first bore.

A piston makes a fluid-sealing, sliding fit in the second bore. A rod attached to the piston extends into the first bore and has a smaller lateral area than that of the second bore. The rod is of a length such as to strike the bore at or beyond the groove inside the first bore, before the piston strikes the body in the second bore. Pressure means is adapted to apply pressure in the second bore so as to move the piston and the rod toward the first bore so that the rod strikes an axial blow on the inside of the neck on the opposite side of the groove from the body thereby to fracture the neck at the groove. Because of the difference in lateral areas of the piston and the rod, there is a heavier unit presure on the neck at the point of fracture than would be the case were the diameters equal.

According to a preferred but optional feature of this invention, the pressure means is an explosive charge which discharges into the second bore on the opposite side of the piston from the first bore.

According to still another preferred but optional feature of the invention, the first bore has a smaller lateral area than that of the second bore and makes a close fitting sliding contact with the rod so as to the rod.

According to another to give lateral support preferred but optional feature of the invention, the presure means comprises a third bore in the body, which third bore has a greater lateral area than that of the second bore, there being a second piston in fluid-sealing, sliding relationship in the third bore. A second rod is attached to the second piston, this second rod making a sliding, fluid-sealing contact with a fluid extens1on of the second bore, the fluid extension having a lesser lateral area than that of the third bore. A source of fluld under pressure discharges against the second piston on the opposite side thereof from the first piston whereby the pressure in the second bore exceeds that of the pressure source.

The above and other features of this invention will be fully understood from the following detailed description and the accompanying drawings in which:

FIG. 1 is a side elevation of the invention showing an application thereof;

FIG. 2 is a fragmentary axial cross-section of FIG. 1;

FIG. 3 is a left-hand end view of FIG. 2;

FIG. 4 is a fragmentary axial cross-section showing the device of FIG. 1 after actuation;

k FIG. 5 is a side view of another embodiment of the invention;

FIG. 6 is a side elevation partly in cutaway cross-section showing the presently preferred embodiment of the lnvention;

FIG. 7 is a left-hand end view of FIG. 6; and

FIG. 8 is a cross-section taken at line 88 of FIG. 6.

FIG. 1 shows a separable bolt 10 according to the invention holding together the ends of a band 11 by means of loops 12, 13. The loops are apertured to pass the bolt. Loop 12 bears against a face 14 on the bolt. A nut 15 is threaded onto the bolt, and the two loops are held together with the bolt in tension.

As can best be seen in FIG. 2, the separable bolt has a body 16 which incorporates a neck 17 that projects away from the body along axis 18. The neck is initially formed separately from the main portion of the body. The two parts are joined together by thread 19 which is locked by pin 20. Thread 21 is formed on the outside of the neck to receive nut 15. If desired, a second thread 22 may be formed on the neck closer to the body. The neck and body may be formed in a single piece, if preferred.

A first bore 25 extends axially through the body and into the neck along axis 18. It terminates adjacent to a groove 26. The term groove is used in its broadest sense herein as indicating a region of reduced thickness adjacent to a region of greater thickness. In the arrangement shown in FIG. 1, a conical fracture zone 27 is formed between the bore and the groove. Had the bore been located farther to the left, then the fracture zone would have been closer to a flat annulus. At any event, the groove is so disposed relative to the bore that, with the bore, it forms a region of reduced cross-section area, and thereby a fracture zone where the bolt will separate.

A second bore 30 is formed in the body which is in fluid communication with the first bore. A first piston 31 makes a sliding, fluid-sealing fit in the wall of the second bore. An O-ring 32 forms the fluid seal. A first rod 33 is attached to the first piston and extends into the first bore. The rod is sufliciently long that it can contact the neck at the end of the bore before the piston strikes the right-hand end of the second bore. Therefore, there is freedom for the piston to move in its bore even though the rod bears against the neck in the bore.

A squib port 34 is internally threaded, and in fluid communication with the second bore on the side of the first piston opposite from rod 33. Pressure means 35 is adapted to supply pressure to the side of the first piston.

The preferred embodiment of pressure means comprises an explosive squib 36 which may be threaded into squib port 34 so as to discharge fluid under pressure into this port when the squib is initiated. Electric leads 37 connect the squib to a source of electricity which will initiate the squib. Pressure means other than squibs may be utilized such as cartridges containing compressed gas. Also numerous types of squibs may be utilized. A well-known and suitable example of such a squib is shown in United States Patent No. 3,135,200 issued to Jackson on June 2, 1964.

FIG. shows a separable bolt 40 having a body 41 that includes a neck 42 with a thread 43 on one side of groove 44 and an abutment 45 on the other side of the groove, indicating that second thread 22 of FIG. 1 is optional.

The presently preferred embodiment of the invention is shown in FIG. 6 wherein a separable bolt is shown holding plates 51, 52 together by means of a nut 53 attached totherads 54.

The bolt includes a body 55 having a neck 56. The neck comprises an extension of the body and is attached to the left-hand portion of the body in FIG. 6 by threads 57, which may be locked by any desired means. The plates being held together abut a face 58 of the body and are held against it by nut 53. The function of the device is to hold two objects together, and then separate at groove 59 when the device is actuated.

A first bore 60 extends along axis 61 into the neck and terminates axially near groove 59 so as to form a region of reduced cross-section. A second bore 62 is in fluid communication with the first bore and accommodates a first piston 63 from which a first rod 64 projects into the first bore. The rod preferably but not necessarily makes a close sliding fit in the first bore so that the rod is supported laterally and will not bend or undergo column failure under the forces exerted on it. However, it will be noted that the force against the neck as exerted by the rod is that of a physical contact rather than that of a fluid pressure contact, so that the lateral area of the first bore is immaterial as to force transmission except, of course, as it relates to the cross-sectional area of the region of least strength. The lateral area of the rod is less than that of the first piston. The length of the first rod is such that it can strike the end of the bore in the neck before the piston strikes the right-hand end of the second bore. An 0- ring 65 makes a sliding, fluid-sealing fit between the first piston and the wall of the second bore.

To the left of the second bore is a pressure means which includes a third bore 66 having a larger lateral area than the rod. A second piston 67 makes a sliding, fluid-sealing fit with the wall of the third bore and carries with it a second rod 68. Rod 68 slides in a fluid extension 69 of the second bore. Its lateral area is less than that of the third bore. The fluid extension 69 is preferably a cylindrical region and is sometimes hereinafter referred to as a fourth bore. Preferably, but not necessarily, its lateral area should be less than that of the second bore.

A plastic material 70 fills the fourth bore and that region of the second bore to the left of the first piston, whereby pressure in the fourth bore is communicated to the second bore. Any desired fluid material may be utilized for this purpose, the term fluid referring to the capacity to readily change shape and transmit pressure such as is typical of liquids or materials which behave as liquids under pressure, such a silicone rubbers. Any suitable inert liquid will also serve, such as water or oil. Preferably, a semi-solid material such as a silicone rubber will be used in order to minimize the danger of leakage and to extend the storage life of the device.

A source of fluid under pressure is provided at the left-hand end of the second piston. In this case, it is a squib 76 like squib 36 in FIG. 1. However, instead of being a separate unit threaded to the body as in FIG. 1,

4 squib 76 is formed integrally with the body. Shield 77 provides protection for electrodes 78 and means for attachment to other structure.

The principal distinction between FIGS. 1 and 6 is that in FIG. 1, the pressure means comprises solely the squib, while in FIG. 6, the pressure means comprises not only the squib but the third and fourth bore and the second piston and rod which can provide additional amplification of the pressure from the source. The general design criteria of the devices of FIGS. 1, 5 and 6 are identical.

The operation of the device of FIG. 1 should be evident from the foregoing. With the device in the condition shown in FIG. 1, the loops 12, 13 may be held together so as to hold the band in place, it being understood that this is simply one example of many applications of the device. When the squib is fired, a substantial pressure is developed in the second bore and exerted on the lefthand face of first piston 31. The force, that is, the product of the pressure and the lateral area of the piston is conveyed to the rod which exerts a strong axial force to the right on the neck spaced from the body. This force causes the neck to fail in the fracture zone which terminates at the groove and the device separates. It is immaterial whether the rod strikes the neck or bears against it initially and simply transmits the sudden load exerted on it. The device of FIG. 5 operates the same as that of FIG. 1, the difference between the two embodiments being their adaptation for holding bodies together.

FIG. 6 shows a technique for amplifying the pressure of the squib. This pressure is exerted over the left-hand face of the second piston, thereby to create a force defined by the product of the lateral area of the piston and the fluid force developed by the squib. This total force is exerted on the lesser area of the fourth bore which in turn is applied in the second bore against the first piston. This amplifies the pressure on the second piston, making this pressure higher than that of the squib. In turn, this pressure is transmitted as an additionally amplified force through the first rod, which causes the separation as hereinbefore stated in connection with the device of FIG. 1.

The device of FIG. 6 has the additional advantage of containing the gases which it generates.

The design criteria of the relative lateral areas of the bores in the embodiments should be evident from the foregoing, these being determined by the amplification desired, if any, or from the force needed to fracture the neck. It is evident that substantial forces may be ex erted in the bores and transmitted as large forces by a relatively small, laterally confined rod. Were such large forces to be exerted by an explosive placed inside a cavity at the fracture zone, then the cavity would have to be very large, limiting the strength of the neck at the fracture zone. Also, there would be hoop forces tending to expand the neck which might tend to hold it into surrounding structure, which might not be desirable. It is also evident that lower gas pressures and lesser explosive charges can be used, relying on the amplifying effect of the piston-rod combinations. This invention therefore provides a very wide range of design alternatives.

The term lateral area as used herein is intended to comprise the area of a region subjected to pressure taken on a plane normal to the axis of the body.

This invention is not to be limited by the embodiments shown in the drawings and described in the description which are given by way of example and not of limitation.

What is claimed is:

1. A separable bolt comprising: a body having a first and a second bore, both of said bores having an axis and being coaxial, said bores also being interconnected; a neck on said body forming a bolt, the first bore extending into the neck; a groove formed in the neck at least partially axially aligned with the first bore to form a region of reduced cross-section in the neck; a piston making a fluid sealing, sliding fit in the second bore; a rod attached to said piston and extending into said first bore, said rod being of such a length as to strike the neck inside the first bore at or beyond the groove before the piston strikes the body in the second bore, and of smaller lateral area than the second bore; pressure means adapted to apply pressure in the second bore to move the piston and rod toward the first bore, so that the rod strikes an axial blow on the inside of the neck, on the opposite side of the groove from the body, thereby to fracture the neck at the groove by failure of the neck in tension, said pressure means comprising a third bore in the body, which third bore has a greater lateral area than that of the second bore, a second piston in fluid sealing, sliding relationship in the third bore, a second rod attached to the second piston, said second rod making a sliding fluid sealing contact with a fluid extension of the second bore of lesser lateral area than that of the third bore, a first fluid filling the said extension between the second rod and the first piston, and a source of second fluid under pressure discharging against the second piston on the opposite side thereof from said first fluid, whereby the pressure generated in the second bore exceeds that generated by the source of second fluid.

2. A separable bolt according to claim 1 in which the said fluid extension comprises a fourth bore having a lesser lateral area than that of the second bore, all of the bores being coaxial.

3. A separable bolt according to claim 1 in which the said source is an explosive charge.

4. A separable bolt according to claim 2 in which the said source is an explosive charge.

5. A separable bolt according to claim 2 in which attachment means is carried by the neck on the side of the groove away from the body.

6. A separable bolt according to claim 5 in which the attachment means comprises a thread.

References Cited UNITED STATES PATENTS 2,892,452 6/1959 Weinstock.

3,084,597 4/1963 Beyer 89--1 3,196,745 7/1965 Sustrich et a1. 89-1 2,653,504 9/1953 Smith 1 CARL W. TOMLIN, Primary Examiner. RAMON S. BRITTS, Assistant Examiner.

U.S. Cl. X.R. 

